Streptococcus pneumoniae is often isolated from patients with community-acquired
pneumonia.
Antibiotics are the primary line of treatment for
pneumococcal pneumonia; however, rising antimicrobial resistance is becoming more prevalent.
Hinokitiol, which is isolated from trees in the cypress family, has been demonstrated to exert antibacterial activity against S. pneumoniae in vitro regardless of antimicrobial resistance. In this study, the efficacy of
hinokitiol was investigated in a mouse
pneumonia model. Male 8-week-old BALB/c mice were intratracheally infected with S. pneumoniae strains D39 (antimicrobial susceptible) and NU4471 (
macrolide resistant). After 1 h,
hinokitiol was injected via the tracheal route.
Hinokitiol significantly decreased the number of S. pneumoniae in the bronchoalveolar lavage fluid (BALF) and the concentration of pneumococcal
DNA in the serum, regardless of whether bacteria were resistant or susceptible to
macrolides. In addition,
hinokitiol decreased the infiltration of neutrophils in the lungs, as well as the concentration of inflammatory
cytokines in the BALF and serum. Repeated
hinokitiol injection at 18 h intervals showed downward trend in the number of S. pneumoniae in the BALF and the concentration of S. pneumoniae
DNA in the serum with the number of
hinokitiol administrations. These findings suggest that
hinokitiol reduced bacterial load and suppressed excessive host immune response in the
pneumonia mouse model. Accordingly,
hinokitiol warrants further exploration as a potential candidate for the treatment of
pneumococcal pneumonia.